The application of coherent adaptive optical systems for target tracking has been described in U.S. Pat. No. 3,877,813 issued to Cecil L. Hayes et al for Self-Compensating Interferometer. In such application, a single transmitting laser oscillator and associated optics cooperate to provide a multiple beam laser system array as a large near-field aperture to provide a narrow far-field beam. In this way, a maximum concentration of energy per unit area is provided for illumination of reflective targets of minimum size or at maximum range, as is well understood in the art. It is also understood that the effectiveness of such array requires a preselected phase distribution across the near-field aperture defined by such array. Focusing or aperture distribution control of the multiple beams comprising the composite beam of such array is achieved by discrete phase adjustment of the separate optics employed for each transmitted beam comprising the array. In the system disclosed in the above-noted U.S. Pat. No. 3,877,813, in which the same aperture optics serves as both transmitter of illumination and receiver of target reflections thereof, phase shifters in the optical paths of the multiple beam optics are compensatorily adjusted to reduce the detected phase difference between a reference received beam and each of the other received beams. In this way, the multiple beams transmitted by such optics are also adjusted so as to achieve such focusing. A second type of compensatory phase-distribution control for a sub-aperture, multiple beam transmitter employing a single transmitter laser oscillator, but employing a separate and single receiving optical element, is shown in FIG. 3 of U.S. Pat. No. 3,731,103 issued to O'Meara for Adaptive Arrays, while the use of a separate array of receiver beam splitters and single local oscillator for phase front adjustment of an array of receiving optics is shown by FIG. 5 of such latter reference.
In a case requiring increased illumination of the target or detection thereof at increased ranges, an array of several transmitting laser oscillators, each with its own multiple beam optics, may be desired. In other words, that focusing upon and tracking of a target described in U.S. Pat. No. 3,877,813 may call for a plurality of the systems described in such patent to describe the overall system aperture, the multiple beams of each system comprising a sub-aperture thereof. Although the multiple beams of each such transmitting laser or subsystem may be mutually phase-tracking, yet the separate subapertures defined by the separate multiple beam subsystem may not be mutually phase-tracking, but instead are subject to the differential phase-drift or randomness among the separate laser transmitters for such separate multiple beam subsystems.